The World Health Organization at its 1978 international conference held in the Soviet Union produced the Alma-Ata Health Declaration, which was designed to serve governments as a basis for planning health care that would reach people at all levels of society. The declaration reaffirmed that “health, which is a state of complete physical, mental and social well-being, and not merely the absence of disease or infirmity, is a fundamental human right and that the attainment of the highest possible level of health is a most important world-wide social goal whose realization requires the action of many other social and economic sectors in addition to the health sector.” In its widest form the practice of medicine, that is to say the promotion and care of health, is concerned with this ideal.

It is generally the goal of most countries to have their health services organized in such a way to ensure that individuals, families, and communities obtain the maximum benefit from current knowledge and technology available for the promotion, maintenance, and restoration of health. In order to play their part in this process, governments and other agencies are faced with numerous tasks, including the following: (1) They must obtain as much information as is possible on the size, extent, and urgency of their needs; without accurate information, planning can be misdirected. (2) These needs must then be revised against the resources likely to be available in terms of money, manpower, and materials; developing countries may well require external aid to supplement their own resources. (3) Based on their assessments, countries then need to determine realistic objectives and draw up plans. (4) Finally, a process of evaluation needs to be built into the program; the lack of reliable information and accurate assessment can lead to confusion, waste, and inefficiency.

Health services of any nature reflect a number of interrelated characteristics, among which the most obvious, but not necessarily the most important from a national point of view, is the curative function; that is to say, caring for those already ill. Others include special services that deal with particular groups (such as children or pregnant women) and with specific needs such as nutrition or immunization; preventive services, the protection of the health both of individuals and of communities; health education; and, as mentioned above, the collection and analysis of information.

In the curative domain there are various forms of medical practice. They may be thought of generally as forming a pyramidal structure, with three tiers representing increasing degrees of specialization and technical sophistication but catering to diminishing numbers of patients as they are filtered out of the system at a lower level. Only those patients who require special attention either for diagnosis or treatment should reach the second (advisory) or third (specialized treatment) tiers where the cost per item of service becomes increasingly higher. The first level represents primary health care, or first contact care, at which patients have their initial contact with the health-care system.

Primary health care is an integral part of a country's health maintenance system, of which it forms the largest and most important part. As described in the declaration of Alma-Ata, primary health care should be “based on practical, scientifically sound and socially acceptable methods and technology made universally accessible to individuals and families in the community through their full participation and at a cost that the community and country can afford to maintain at every stage of their development.” Primary health care in the developed countries is usually the province of a medically qualified physician; in the developing countries first contact care is often provided by nonmedically qualified personnel.

The vast majority of patients can be fully dealt with at the primary level. Those who cannot are referred to the second tier (secondary health care, or the referral services) for the opinion of a consultant with specialized knowledge or for X-ray examinations and special tests. Secondary health care often requires the technology offered by a local or regional hospital. Increasingly, however, the radiological and laboratory services provided by hospitals are available directly to the family doctor, thus improving his service to patients and increasing its range. The third tier of health care, employing specialist services, is offered by institutions such as teaching hospitals and units devoted to the care of particular groups—women, children, patients with mental disorders, and so on. The dramatic differences in the cost of treatment at the various levels is a matter of particular importance in developing countries, where the cost of treatment for patients at the primary health-care level is usually only a small fraction of that at the third level; medical costs at any level in such countries, however, are usually borne by the government.

Ideally, provision of health care at all levels will be available to all patients; such health care may be said to be universal. The well-off, both in relatively wealthy industrialized countries and in the poorer developing world, may be able to get medical attention from sources they prefer and can pay for in the private sector. The vast majority of people in most countries, however, are dependent in various ways upon health services provided by the state, to which they may contribute comparatively little or, in the case of poor countries, nothing at all.

The costs to national economics of providing health care are considerable and have been growing at a rapidly increasing rate, especially in countries such as the United States, Germany, and Sweden; the rise in Britain has been less rapid. This trend has been the cause of major concerns in both developed and developing countries. Some of this concern is based upon the lack of any consistent evidence to show that more spending on health care produces better health. There is a movement in developing countries to replace the type of organization of health-care services that evolved during European colonial times with some less expensive, and for them, more appropriate, health-care system.

In the industrialized world the growing cost of health services has caused both private and public health-care delivery systems to question current policies and to seek more economical methods of achieving their goals. Despite expenditures, health services are not always used effectively by those who need them, and results can vary widely from community to community. In Britain, for example, between 1951 and 1971 the death rate fell by 24 percent in the wealthier sections of the population but by only half that in the most underprivileged sections of society. The achievement of good health is reliant upon more than just the quality of health care. Health entails such factors as good education, safe working conditions, a favourable environment, amenities in the home, well-integrated social services, and reasonable standards of living.

The developing countries differ from one another culturally, socially, and economically, but what they have in common is a low average income per person, with large percentages of their populations living at or below the poverty level. Although most have a small elite class, living mainly in the cities, the largest part of their populations live in rural areas. Urban regions in developing and some developed countries in the mid- and late 20th century have developed pockets of slums, which are growing because of an influx of rural peoples. For lack of even the simplest measures, vast numbers of urban and rural poor die each year of preventable and curable diseases, often associated with poor hygiene and sanitation, impure water supplies, malnutrition, vitamin deficiencies, and chronic preventable infections. The effect of these and other deprivations is reflected by the finding that in the 1980s the life expectancy at birth for men and women was about one-third less in Africa than it was in Europe; similarly, infant mortality in Africa was about eight times greater than in Europe. The extension of primary health-care services is therefore a high priority in the developing countries.

The developing countries themselves, lacking the proper resources, have often been unable to generate or implement the plans necessary to provide required services at the village or urban poor level. It has, however, become clear that the system of health care that is appropriate for one country is often unsuitable for another. Research has established that effective health care is related to the special circumstances of the individual country, its people, culture, ideology, and economic and natural resources.

The rising costs of providing health care have influenced a trend, especially among the developing nations, to promote services that employ less highly trained primary health-care personnel who can be distributed more widely in order to reach the largest possible proportion of the community. The principal medical problems to be dealt with in the developing world include undernutrition, infection, gastrointestinal disorders, and respiratory complaints, which themselves may be the result of poverty, ignorance, and poor hygiene. For the most part, these are easy to identify and to treat. Furthermore, preventive measures are usually simple and cheap. Neither treatment nor prevention requires extensive professional training: in most cases they can be dealt with adequately by the “primary health worker,” a term that includes all nonprofessional health personnel.

Those concerned with providing health care in the developed countries face a different set of problems. The diseases so prevalent in the Third World have, for the most part, been eliminated or are readily treatable. Many of the adverse environmental conditions and public health hazards have been conquered. Social services of varying degrees of adequacy have been provided. Public funds can be called upon to support the cost of medical care, and there are a variety of private insurance plans available to the consumer. Nevertheless, the funds that a government can devote to health care are limited and the cost of modern medicine continues to increase, thus putting adequate medical services beyond the reach of many. Adding to the expense of modern medical practices is the increasing demand for greater funding of health education and preventive measures specifically directed toward the poor.

In many parts of the world, particularly in developing countries, people get their primary health care, or first-contact care, where available at all, from nonmedically qualified personnel; these cadres of medical auxiliaries are being trained in increasing numbers to meet overwhelming needs among rapidly growing populations. Even among the comparatively wealthy countries of the world, containing in all a much smaller percentage of the world's population, escalation in the costs of health services and in the cost of training a physician has precipitated some movement toward reappraisal of the role of the medical doctor in the delivery of first-contact care.

In advanced industrial countries, however, it is usually a trained physician who is called upon to provide the first-contact care. The patient seeking first-contact care can go either to a general practitioner or turn directly to a specialist. Which is the wisest choice has become a subject of some controversy. The general practitioner, however, is becoming rather rare in some developed countries. In countries where he does still exist, he is being increasingly observed as an obsolescent figure, because medicine covers an immense, rapidly changing, and complex field of which no physician can possibly master more than a small fraction. The very concept of the general practitioner, it is thus argued, may be absurd.

The obvious alternative to general practice is the direct access of a patient to a specialist. If a patient has problems with vision, he goes to an eye specialist, and if he has a pain in his chest (which he fears is due to his heart), he goes to a heart specialist. One objection to this plan is that the patient often cannot know which organ is responsible for his symptoms, and the most careful physician, after doing many investigations, may remain uncertain as to the cause. Breathlessness—a common symptom—may be due to heart disease, to lung disease, to anemia, or to emotional upset. Another common symptom is general malaise—feeling run-down or always tired; others are headache, chronic low backache, rheumatism, abdominal discomfort, poor appetite, and constipation. Some patients may also be overtly anxious or depressed. Among the most subtle medical skills is the ability to assess people with such symptoms and to distinguish between symptoms (psychosomatic disorder) that are caused predominantly by emotional upset and those that are predominantly of bodily origin. A specialist may be capable of such a general assessment, but, often, with emphasis on his own subject, he fails at this point. The generalist with his broader training is often the better choice for a first diagnosis, with referral to a specialist as the next option.

It is often felt that there are also practical advantages for the patient in having his own doctor, who knows about his background, who has seen him through various illnesses, and who has often looked after his family as well. This personal physician, often a generalist, is in the best position to decide when the patient should be referred to a consultant.

The advantages of general practice and specialization are combined when the physician of first contact is a pediatrician (pediatrics). Although he sees only children and thus acquires a special knowledge of childhood maladies, he remains a generalist who looks at the whole patient. Another combination of general practice and specialization is represented by group practice, the members of which partially or fully specialize. One or more may be general practitioners, and one may be a surgeon, a second an obstetrician, a third a pediatrician, and a fourth an internist. In isolated communities group practice may be a satisfactory compromise, but in urban regions, where nearly everyone can be sent quickly to a hospital, the specialist surgeon working in a fully equipped hospital can usually provide better treatment than a general practitioner surgeon in a small clinic hospital.

Before 1948, general practitioners in Britain settled where they could make a living. Patients fell into two main groups: weekly wage earners, who were compulsorily insured, were on a doctor's “panel” and were given free medical attention (social service) (for which the doctor was paid quarterly by the government); most of the remainder paid the doctor a fee for service at the time of the illness. In 1948 the National Health Service began operation. Under its provisions, everyone is entitled to free medical attention with a general practitioner with whom he is registered. Though general practitioners in the National Health Service are not debarred from also having private patients, these must be people who are not registered with them under the National Health Service. Any physician is free to work as a general practitioner entirely independent of the National Health Service, though there are few who do so. Almost the entire population is registered with a National Health Service general practitioner, and the vast majority automatically sees this physician, or one of his partners, when they require medical attention. A few people (social class), mostly wealthy, while registered with a National Health Service general practitioner, regularly see another physician privately; and a few may occasionally seek a private consultation because they are dissatisfied with their National Health Service physician.

A general practitioner under the National Health Service remains an independent contractor, paid by a capitation fee; that is, according to the number of people registered with him. He may work entirely from his own office, and he provides and pays his own receptionist, secretary, and other ancillary staff. Most general practitioners have one or more partners and work more and more in premises built for the purpose. Some of these structures are erected by the physicians themselves, but many are provided by the local authority, the physicians paying rent for using them. Health centres, in which groups of general practitioners work have become common.

In Britain only a small minority of general practitioners can admit patients to a hospital and look after them personally. Most of this minority are in country districts, where, before the days of the National Health Service, there were cottage hospitals run by general practitioners; many of these hospitals continued to function in a similar manner. All general practitioners use such hospital facilities as X-ray departments and laboratories, and many general practitioners work in hospitals in emergency rooms (casualty departments) or as clinical assistants to consultants, or specialists.

General practitioners are spread more evenly over the country than formerly, when there were many in the richer areas and few in the industrial towns. The maximum allowed list of National Health Service patients per doctor is 3,500; the average is about 2,500. Patients have free choice of the physician with whom they register, with the proviso that they cannot be accepted by one who already has a full list and that a physician can refuse to accept them (though such refusals are rare). In remote rural places there may be only one physician within a reasonable distance.

Until the mid-20th century it was not unusual for the doctor in Britain to visit patients in their own homes. A general practitioner might make 15 or 20 such house calls in a day, as well as seeing patients in his office or “surgery,” often in the evenings. This enabled him to become a family doctor in fact as well as in name. In modern practice, however, a home visit is quite exceptional and is paid only to the severely disabled or seriously ill when other recourses are ruled out. All patients are normally required to go to the doctor.

It has also become unusual for a personal doctor to be available during weekends or holidays. His place may be taken by one of his partners in a group practice, a provision that is reasonably satisfactory. General practitioners, however, may now use one of several commercial deputizing services that employs young doctors to be on call. Although some of these young doctors may be well experienced, patients do not generally appreciate this kind of arrangement.

Whereas in Britain the doctor of first contact is regularly a general practitioner, in the United States the nature of first-contact care is less consistent. General practice in the United States has been in a state of decline in the second half of the 20th century, especially in metropolitan areas. The general practitioner, however, is being replaced to some degree by the growing field of family practice. In 1969 family practice was recognized as a medical specialty after the American Academy of General Practice (now the American Academy of Family Physicians) and the American Medical Association created the American Board of General (now Family) Practice. Since that time the field has become one of the larger medical specialties in the United States. The family physicians were the first group of medical specialists in the United States for whom recertification was required.

There is no national health service, as such, in the United States. Most physicians in the country have traditionally been in some form of private practice, whether seeing patients in their own offices, clinics, medical centres, or another type of facility and regardless of the patients' income. Doctors are usually compensated by such state and federally supported agencies as Medicaid (for treating the poor) and Medicare (for treating the elderly); not all doctors, however, accept poor patients. There are also some state-supported clinics and hospitals where the poor and elderly may receive free or low-cost treatment, and some doctors devote a small percentage of their time to treatment of the indigent. Veterans may receive free treatment at Veterans Administration hospitals, and the federal government through its Indian Health Service provides medical services to American Indians and Alaskan natives, sometimes using trained auxiliaries for first-contact care.

In the rural United States first-contact care is likely to come from a generalist. The middle- and upper-income groups living in urban areas, however, have access to a larger number of primary medical care options. Children are often taken to pediatricians, who may oversee the child's health needs until adulthood. Adults frequently make their initial contact with an internist, whose field is mainly that of medical (as opposed to surgical) illnesses; the internist often becomes the family physician. Other adults choose to go directly to physicians with narrower specialties, including dermatologists, allergists, gynecologists, orthopedists, and ophthalmologists.

Patients in the United States may also choose to be treated by doctors of osteopathy. These doctors are fully qualified, but they make up only a small percentage of the country's physicians. They may also branch off into specialties, but general practice is much more common in their group than among M.D.'s.

It used to be more common in the United States for physicians providing primary care to work independently, providing their own equipment and paying their own ancillary staff. In smaller cities they mostly had full hospital privileges, but in larger cities these privileges were more likely to be restricted. Physicians, often sharing the same specialties, are increasingly entering into group associations, where the expenses of office space, staff, and equipment may be shared; such associations may work out of suites of offices, clinics, or medical centres. The increasing competition and risks of private practice have caused many physicians to join Health Maintenance Organizations (health maintenance organization) (HMOs), which provide comprehensive medical care and hospital care on a prepaid basis. The cost savings to patients are considerable, but they must use only the HMO doctors and facilities. HMOs stress preventive medicine and out-patient treatment as opposed to hospitalization as a means of reducing costs, a policy that has caused an increased number of empty hospital beds in the United States.

While the number of doctors per 100,000 population in the United States has been steadily increasing, there has been a trend among physicians toward the use of trained medical personnel to handle some of the basic services normally performed by the doctor. So-called physician extender services are commonly divided into nurse practitioners and physician's assistants, both of whom provide similar ancillary services for the general practitioner or specialist. Such personnel do not replace the doctor. Almost all American physicians have systems for taking each other's calls when they become unavailable. House calls in the United States, as in Britain, have become exceedingly rare.

In Russia general practitioners are prevalent in the thinly populated rural areas. Pediatricians deal with children up to about age 15. Internists look after the medical ills of adults, and occupational physicians deal with the workers, sharing care with internists.

Teams of physicians with experience in varying specialties work from polyclinics or outpatient units, where many types of diseases are treated. Small towns usually have one polyclinic to serve all purposes. Large cities commonly have separate polyclinics for children and adults, as well as clinics with specializations such as women's health care, mental illnesses, and sexually transmitted diseases. Polyclinics usually have X-ray apparatus and facilities for examination of tissue specimens, facilities associated with the departments of the district hospital. Beginning in the late 1970s was a trend toward the development of more large, multipurpose treatment centres, first-aid hospitals, and specialized medicine and health care centres.

Home visits have traditionally been common, and much of the physician's time is spent in performing routine checkups for preventive (preventive medicine) purposes. Some patients in sparsely populated rural areas may be seen first by feldshers (auxiliary health workers), nurses, or midwives who work under the supervision of a polyclinic or hospital physician. The feldsher was once a lower-grade physician in the army or peasant communities, but feldshers are now regarded as paramedical workers.

In Japan, with less rigid legal restriction of the sale of pharmaceuticals than in the West, there was formerly a strong tradition of self-medication and self-treatment. This was modified in 1961 by the institution of health insurance programs that covered a large proportion of the population; there was then a great increase in visits to the outpatient clinics of hospitals and to private clinics and individual physicians.

When Japan shifted from traditional Chinese medicine with the adoption of Western medical practices in the 1870s, Germany became the chief model. As a result of German influence and of their own traditions, Japanese physicians tended to prefer professorial status and scholarly research opportunities at the universities or positions in the national or prefectural hospitals to private practice. There were some pioneering physicians, however, who brought medical care to the ordinary people.

Physicians in Japan have tended to cluster in the urban areas. The Medical Service Law of 1963 was amended to empower the Ministry of Health and Welfare to control the planning and distribution of future public and nonprofit medical facilities, partly to redress the urban-rural imbalance. Meanwhile, mobile services were expanded.

The influx of patients into hospitals and private clinics after the passage of the national health insurance acts of 1961 had, as one effect, a severe reduction in the amount of time available for any one patient. Perhaps in reaction to this situation, there has been a modest resurgence in the popularity of traditional Chinese medicine, with its leisurely interview, its dependence on herbal and other “natural” medicines, and its other traditional diagnostic and therapeutic practices. The rapid aging of the Japanese population as a result of the sharply decreasing death rate and birth rate has created an urgent need for expanded health care services for the elderly. There has also been an increasing need for centres to treat health problems resulting from environmental causes.

On the continent of Europe there are great differences both within single countries and between countries in the kinds of first-contact medical care. General practice, while declining in Europe as elsewhere, is still rather common even in some large cities, as well as in remote country areas.

In The Netherlands (Netherlands, The), departments of general practice are administered by general practitioners in all the medical schools—an exceptional state of affairs—and general practice flourishes. In the larger cities of Denmark, general practice on an individual basis is usual and popular, because the physician works only during office hours. In addition, there is a duty doctor service for nights and weekends. In the cities of Sweden, primary care is given by specialists. In the remote regions of northern Sweden, district doctors act as general practitioners to patients spread over huge areas; the district doctors delegate much of their home visiting to nurses.

In France there are still general practitioners, but their number is declining. Many medical practitioners advertise themselves directly to the public as specialists in internal medicine, ophthalmologists, gynecologists, and other kinds of specialists. Even when patients have a general practitioner, they may still go directly to a specialist. Attempts to stem the decline in general practice are being made by the development of group practice and of small rural hospitals equipped to deal with less serious illnesses, where general practitioners can look after their patients.

Although Israel has a high ratio of physicians to population, there is a shortage of general practitioners, and only in rural areas is general practice common. In the towns many people go directly to pediatricians, gynecologists, and other specialists, but there has been a reaction against this direct access to the specialist. More general practitioners have been trained, and the Israel Medical Association has recommended that no patient should be referred to a specialist except by the family physician or on instructions given by the family nurse. At Tel Aviv University there is a department of family medicine. In some newly developing areas, where the doctor shortage is greatest, there are medical centres at which all patients are initially interviewed by a nurse (nursing). The nurse may deal with many minor ailments, thus freeing the physician to treat the more seriously ill.

Nearly half the medical doctors in Australia are general practitioners—a far higher proportion than in most other advanced countries—though, as elsewhere, their numbers are declining. They tend to do far more for their patients than in Britain, many performing such operations as removal of the appendix, gallbladder, or uterus, operations that elsewhere would be carried out by a specialist surgeon. Group practices are common.

Throughout China the value of traditional medicine is stressed, especially in the rural areas. All medical schools are encouraged to teach traditional medicine as part of their curriculum, and efforts are made to link colleges of Chinese medicine with Western-type medical schools. Medical education is of shorter duration than it is in Europe, and there is greater emphasis on practical work. Students spend part of their time away from the medical school working in factories or in communes; they are encouraged to question what they are taught and to participate in the educational process at all stages. One well-known form of traditional medicine is acupuncture, which is used as a therapeutic and pain-relieving technique; requiring the insertion of brass-handled needles at various points on the body, acupuncture has become quite prominent as a form of anesthesia.

The vast number of nonmedically qualified health staff, upon whom the health-care system greatly depends, includes both full-time and part-time workers. The latter include so-called barefoot doctors, who work mainly in rural areas, worker doctors in factories, and medical workers in residential communities. None of these groups is medically qualified. They have had only a three-month period of formal training, part of which is done in a hospital, fairly evenly divided between theoretical and practical work. This is followed by a varying period of on-the-job experience under supervision.

Āyurvedic medicine is an example of a well-organized system of traditional health care, both preventive and curative, that is widely practiced in parts of Asia. Āyurvedic medicine has a long tradition behind it, having originated in India perhaps as long as 3,000 years ago. It is still a favoured form of health care in large parts of the Eastern world, especially in India, where a large percentage of the population use this system exclusively or combined with modern medicine. The Indian Medical Council was set up in 1971 by the Indian government to establish maintenance of standards for undergraduate and postgraduate education. It establishes suitable qualifications in Indian medicine and recognizes various forms of traditional practice including Āyurvedic, Unani, and Siddha. Projects have been undertaken to integrate the indigenous Indian and Western forms of medicine. Most Āyurvedic practitioners work in rural areas, providing health care to at least 500,000,000 people in India alone. They therefore represent a major force for primary health care, and their training and deployment are important to the government of India.

Like scientific medicine, Āyurvedic medicine has both preventive and curative aspects. The preventive component emphasizes the need for a strict code of personal and social hygiene, the details of which depend upon individual, climatic, and environmental needs. Bodily exercises, the use of herbal preparations, and Yoga form a part of the remedial measures. The curative aspects of Āyurvedic medicine involves the use of herbal medicines, external preparations, physiotherapy, and diet. It is a principle of Āyurvedic medicine that the preventive and therapeutic measures be adapted to the personal requirements of each patient.

A main goal of the World Health Organization (WHO), as expressed in the Alma-Ata Declaration of 1978, is to provide to all the citizens of the world a level of health that will allow them to lead socially and economically productive lives by the year 2000. By the late 1980s, however, vast disparities in health care still existed between the rich and poor countries of the world. In developing countries such as Ethiopia, Guinea, Mali, and Mozambique, for instance, governments in the late 1980s spent less than $5 per person per year on public health, while in most western European countries several hundred dollars per year was spent on each person. The disproportion of the number of physicians available between developing and developed countries is similarly wide.

Along with the shortage of physicians, there is a shortage of everything else needed to provide medical care—of equipment, drugs, and suitable buildings, and of nurses, technicians, and all other grades of staff, whose presence is taken for granted in the affluent societies. Yet there are greater percentages of sick in the poor countries than in the rich countries. In the poor countries a high proportion of people are young, and all are liable to many infections, including tuberculosis, syphilis, typhoid, and cholera (which, with the possible exception of syphilis, are now rare in the rich countries), and also malaria, yaws, worm infestations, and many other conditions occurring primarily in the warmer climates. Nearly all of these infections respond to the antibiotics and other drugs that have been discovered since the 1920s. There is also much malnutrition and anemia, which can be cured if funding is available. There is a prevalence of disorders remediable by surgery. Preventive medicine can ensure clean water supplies, destroy insects that carry infections, teach hygiene, and show how to make the best use of resources.

In most poor countries there are a few people, usually living in the cities, who can afford to pay for medical care, and in a free market system the physicians tend to go where they can make the best living; this situation causes the doctor–patient ratio to be much higher in the towns than in country districts. A physician in Bombay or in Rio de Janeiro, for example, may have equipment as lavish as that of a physician in the United States and can earn an excellent income. The poor, however, both in the cities and in the country, can get medical attention only if it is paid for by the state, by some supranational body, or by a mission or other charitable organization. Moreover, the quality of the care they receive is often poor, and in remote regions it may be lacking altogether. In practice, hospitals run by a mission may cooperate closely with state-run health centres.

Because physicians are scarce, their skills must be used to best advantage, and much of the work normally done by physicians in the rich countries has to be delegated to auxiliaries or nurses, who have to diagnose the common conditions, give treatment, take blood samples, help with operations, supply simple posters containing health advice, and carry out other tasks. In such places the doctor has time only to perform major operations and deal with the more difficult medical problems. People are treated as far as possible on an outpatient basis from health centres (hospital) housed in simple buildings; few can travel except on foot, and, if they are more than a few miles from a health centre, they tend not to go there. Health centres also may be used for health education.

Although primary health-care service differs from country to country, that developed in Tanzania is representative of many that have been devised in largely rural developing countries. The most important feature of the Tanzanian rural health service is the rural health centre, which, with its related dispensaries, is intended to provide comprehensive health services for the community. The staff is headed by the assistant medical officer and the medical assistant. The assistant medical officer has at least four years of experience, which is then followed by further training for 18 months. He is not a doctor but serves to bridge the gap between medical assistant and physician. The medical assistant has three years of general medical education. The work of the rural health centres and dispensaries is mainly of three kinds: diagnosis and treatment, maternal and child health, and environmental health. The main categories of primary health workers also include medical aids, maternal and child health aids, and health auxiliaries. Nurses and midwives form another category of worker. In the villages there are village health posts staffed by village medical helpers working under supervision from the rural health centre.

In some primitive elements of the societies of developing countries, and of some developed countries, there exists the belief that illness comes from the displeasure of ancestral gods and evil spirits, from the malign influence of evilly disposed persons, or from natural phenomena that can neither be forecast nor controlled. To deal with such causes there are many varieties of indigenous healers who practice elaborate rituals on behalf of both the physically ill and the mentally afflicted. If it is understood that such beliefs, and other forms of shamanism, may provide a basis upon which health care can be based, then primary health care may be said to exist almost everywhere. It is not only easily available but also readily acceptable, and often preferred, to more rational methods of diagnosis and treatment. Although such methods may sometimes be harmful, they may often be effective, especially where the cause is psychosomatic. Other patients, however, may suffer from a disease for which there is a cure in modern medicine.

In order to improve the coverage of primary health-care services and to spread more widely some of the benefits of Western medicine, attempts have sometimes been made to find a means of cooperation, or even integration, between traditional and modern medicine (see above Medical practice in developing countries: India (medicine)). In Africa, for example, some such attempts are officially sponsored by ministries of health, state governments, universities, and the like, and they have the approval of WHO, which often takes the lead in this activity. In view, however, of the historical relationships between these two systems of medicine, their different basic concepts, and the fact that their methods cannot readily be combined, successful merging has been limited.

Persons dissatisfied with the methods of modern medicine or with its results sometimes seek help from those professing expertise in other, less conventional, and sometimes controversial, forms of health care. Such practitioners are not medically qualified unless they are combining such treatments with a regular (allopathic) practice, which includes osteopathy. In many countries the use of some forms, such as chiropractic, requires licensing and a degree from an approved college. The treatments afforded in these various practices are not always subjected to objective assessment, yet they provide services that are alternative, and sometimes complementary, to conventional practice. This group includes practitioners of homeopathy, naturopathy, acupuncture, hypnotism, and various meditative and quasi-religious forms. Numerous persons also seek out some form of faith healing to cure their ills, sometimes as a means of last resort. Religions commonly include some advents of miraculous curing within their scriptures. The belief in such curative powers has been in part responsible for the increasing popularity of the television, or “electronic,” preacher in the United States, a phenomenon that involves millions of viewers. Millions of others annually visit religious shrines, such as the one at Lourdes in France, with the hope of being miraculously healed.

At the beginning of World War II it was possible to recognize a number of major medical specialties, including internal medicine, obstetrics and gynecology, pediatrics, pathology, anesthesiology, ophthalmology, surgery, orthopedic surgery, plastic surgery, psychiatry and neurology, radiology, and urology. Hematology was also an important field of study, and microbiology and biochemistry were important medically allied specialties. Since World War II, however, there has been an almost explosive increase of knowledge in the medical sciences as well as enormous advances in technology as applicable to medicine. These developments have led to more and more specialization. The knowledge of pathology has been greatly extended, mainly by the use of the electron microscope; similarly microbiology, which includes bacteriology, expanded with the growth of such other subfields as virology (the study of viruses) and mycology (the study of yeasts and fungi in medicine). Biochemistry, sometimes called clinical chemistry or chemical pathology, has contributed to the knowledge of disease, especially in the field of genetics where genetic engineering has become a key to curing some of the most difficult diseases. Hematology also expanded after World War II with the development of electron microscopy. Contributions to medicine have come from such fields as psychology and sociology especially in such areas as mental disorders and mental handicaps. Clinical pharmacology has led to the development of more effective drugs and to the identification of adverse reactions. More recently established medical specialties are those of preventive medicine, physical medicine and rehabilitation, family practice, and nuclear medicine. In the United States every medical specialist must be certified by a board composed of members of the specialty in which certification is sought. Some type of peer certification is required in most countries.

To provide more efficient service it is not uncommon for a specialist surgeon and a specialist physician to form a team working together in the field of, for example, heart disease. An advantage of this arrangement is that they can attract a highly trained group of nurses, technologists, operating room technicians, and so on, thus greatly improving the efficiency of the service to the patient. Such specialization is expensive, however, and has required an increasingly large proportion of the health budget of institutions, a situation that eventually has its financial effect on the individual citizen. The question therefore arises as to their cost-effectiveness. Governments of developing countries have usually found, for instance, that it is more cost-efficient to provide more people with basic care.

Physicians in developed countries frequently prefer posts in hospitals with medical schools (medical education). Newly qualified physicians want to work there because doing so will aid their future careers, though the actual experience may be wider and better in a hospital without a medical school. Senior physicians seek careers in hospitals with medical schools because consultant, specialist, or professorial posts there usually carry a high degree of prestige. When the posts are salaried, the salaries are sometimes, but not always, higher than in a nonteaching hospital. Usually a consultant who works in private practice earns more when on the staff of a medical school.

In many medical schools there are clinical professors in each of the major specialties—such as surgery, internal medicine, obstetrics and gynecology, and psychiatry—and often of the smaller specialties as well. There are also professors of pathology, radiology, and radiotherapy. Whether professors or not, all doctors in teaching hospitals have the two functions of caring for the sick and educating students. They give lectures and seminars and are accompanied by students on ward rounds.

The Industrial Revolution greatly changed, and as a rule worsened, the health hazards caused by industry, while the numbers at risk vastly increased. In Britain the first small beginnings of efforts to ameliorate the lot of the workers in factories and mines began in 1802 with the passing of the first factory act, the Health and Morals of Apprentices Act. The factory act of 1838, however, was the first truly effective measure in the industrial field. It forbade night work for children and restricted their work hours to 12 per day. Children under 13 were required to attend school. A factory inspectorate was established, the inspectors being given powers of entry into factories and power of prosecution of recalcitrant owners. Thereafter there was a succession of acts with detailed regulations for safety and health in all industries. Industrial diseases were made notifiable, and those who developed any prescribed industrial disease were entitled to benefits.

The situation is similar in other developed countries. Physicians are bound by legal restrictions and must report industrial diseases. The industrial physician's most important function, however, is to prevent industrial diseases. Many of the measures to this end have become standard practice, but, especially in industries working with new substances, the physician should determine if workers are being damaged and suggest preventive measures. The industrial physician may advise management about industrial hygiene and the need for safety devices and protective clothing and may become involved in building design. The physician or health worker may also inform the worker of occupational health hazards.

Modern factories usually have arrangements for giving first aid in case of accidents. Depending upon the size of the plant, the facilities may range from a simple first-aid station to a large suite of lavishly equipped rooms and may include a staff of qualified nurses and physiotherapists and one or perhaps more full-time physicians.

Physicians in industry carry out medical examinations, especially on new employees and on those returning to work after sickness or injury. In addition, those liable to health hazards may be examined regularly in the hope of detecting evidence of incipient damage. In some organizations every employee may be offered a regular medical examination.

When a worker also has a personal physician, there may be doubt, in some cases, as to which physician bears the main responsibility for his health. When someone has an accident or becomes acutely ill at work, the first aid is given or directed by the industrial physician. Subsequent treatment may be given either at the clinic at work or by the personal physician. Because of labour-management difficulties, workers sometimes tend not to trust the diagnosis of the management-hired physician.

During the epoch of the Soviet Union (Union of Soviet Socialist Republics) and the Soviet bloc, industrial health service generally developed more fully in those countries than in the capitalist countries. At the larger industrial establishments in the Soviet Union, polyclinics were created to provide both occupational and general care for workers and their families. Occupational physicians were responsible for preventing occupational diseases and injuries, health screening, immunization, and health education.

In the capitalist countries, on the other hand, no fixed pattern of industrial health service has emerged. Legislation impinges upon health in various ways, including the provision of safety measures, the restriction of pollution, and the enforcement of minimum standards of lighting, ventilation, and space per person. In most of these countries there is found an infinite variety of schemes financed and run by individual firms or, equally, by huge industries. Labour unions have also done much to enforce health codes within their respective industries. In the developing countries there has been generally little advance in industrial medicine.

In many societies special facilities are provided for the health care of pregnant women, mothers, and their young children. The health care needs of these three groups are generally recognized to be so closely related as to require a highly integrated service that includes prenatal care, the birth of the baby, the postnatal period, and the needs of the infant. Such a continuum should be followed by a service attentive to the needs of young children and then by a school health service. Family clinics are common in countries that have state-sponsored health services, such as those in the United Kingdom and elsewhere in Europe. Family health care in some developed countries, such as the United States, is provided for low-income groups by state-subsidized facilities, but other groups defer to private physicians or privately run clinics (clinic).

Prenatal clinics provide a number of elements. There is, first, the care of the pregnant woman, especially if she is in a vulnerable group likely to develop some complication during the last few weeks of pregnancy and subsequent delivery. Many potential hazards, such as diabetes and high blood pressure, can be identified and measures taken to minimize their effects. In developing countries pregnant women are especially susceptible to many kinds of disorders, particularly infections such as malaria. Local conditions determine what special precautions should be taken to ensure a healthy child. Most pregnant women, in their concern to have a healthy child, are receptive to simple health education. The prenatal clinic provides an excellent opportunity to teach the mother how to look after herself during pregnancy, what to expect at delivery, and how to care for her baby. If the clinic is attended regularly, the woman's record will be available to the staff that will later supervise the delivery of the baby; this is particularly important for someone who has been determined to be at risk. The same clinical unit should be responsible for prenatal, natal, and postnatal care as well as for the care of the newborn infants.

Most pregnant women can be safely delivered in simple circumstances without an elaborately trained staff or sophisticated technical facilities, provided that these can be called upon in emergencies. In developed countries it was customary in premodern times for the delivery to take place in the woman's home supervised by a qualified midwife or by the family doctor. By the mid-20th century women, especially in urban areas, usually preferred to have their babies in a hospital, either in a general hospital or in a more specialized maternity hospital. In many developing countries traditional birth attendants supervise the delivery. They are women, for the most part without formal training, who have acquired skill by working with others and from their own experience. Normally they belong to the local community where they have the confidence of the family, where they are content to live and serve, and where their services are of great value. In many developing countries the better training of birth attendants has a high priority. In developed Western countries there has been a trend toward delivery by natural childbirth, including delivery in a hospital without anesthesia, and home delivery.

Postnatal care services are designed to supervise the return to normal of the mother. They are usually given by the staff of the same unit that was responsible for the delivery. Important considerations are the matter of breast- or artificial feeding and the care of the infant. Today the prospects for survival of babies born prematurely or after a difficult and complicated labour, as well as for neonates (recently born babies) with some physical abnormality, are vastly improved. This is due to technical advances, including those that can determine defects in the prenatal stage, as well as to the growth of neonatology as a specialty. A vital part of the family health-care service is the child welfare clinic, which undertakes the care of the newborn. The first step is the thorough physical examination of the child on one or more occasions to determine whether or not it is normal both physically and, if possible, mentally. Later periodic examinations serve to decide if the infant is growing satisfactorily. Arrangements can be made for the child to be protected from major hazards by, for example, immunization and dietary supplements. Any intercurrent condition, such as a chest infection or skin disorder, can be detected early and treated. Throughout the whole of this period mother and child are together, and particular attention is paid to the education of the mother for the care of the child.

A part of the health service available to children in the developed countries is that devoted to child guidance. This provides psychiatric guidance to maladjusted children usually through the cooperative work of a child psychiatrist, educational psychologist, and schoolteacher.

Since the mid-20th century a change has occurred in the population structure in developed countries. The proportion of elderly people has been increasing. Since 1983, however, in most European countries the population growth of that group has leveled off, although it is expected to continue to grow more rapidly than the rest of the population in most countries through the first third of the 21st century. In the late 20th century Japan had the fastest growing elderly population.

Geriatrics, the health care of the elderly, is therefore a considerable burden on health services. In the United Kingdom about one-third of all hospital beds are occupied by patients over 65; half of these are psychiatric patients. The physician's time is being spent more and more with the elderly, and since statistics show that women live longer than men, geriatric practice is becoming increasingly concerned with the treatment of women. Elderly people often have more than one disorder, many of which are chronic and incurable, and they need more attention from health-care services. In the United States there has been some movement toward making geriatrics a medical specialty, but it has not generally been recognized.

Support services for the elderly provided by private or state-subsidized sources include domestic help, delivery of meals, day-care centres, elderly residential homes or nursing homes, and hospital beds either in general medical wards or in specialized geriatric units. The degree of accessibility of these services is uneven from country to country and within countries. In the United States, for instance, although there are some federal programs, each state has its own elderly programs, which vary widely. However, as the elderly become an increasingly larger part of the population their voting rights are providing increased leverage for obtaining more federal and state benefits. The general practitioner or family physician working with visiting health and social workers and in conjunction with the patient's family often form a working team for elderly care.

In the developing world, countries are largely spared such geriatric problems, but not necessarily for positive reasons. A principal cause, for instance, is that people do not live so long. Another major reason is that in the extended family concept, still prevalent among developing countries, most of the caretaking needs of the elderly are provided by the family.

The spectacular improvement in the expectation of life in the affluent countries has been due far more to public health measures than to curative medicine. These public health measures began operation largely in the 19th century. At the beginning of that century, drainage (sewage system) and water supply systems (water-supply system) were all more or less primitive; nearly all the cities of that time had poorer water and drainage systems than Rome had possessed 1,800 years previously. Infected water supplies caused outbreaks of typhoid, cholera, and other waterborne infections (infectious disease). By the end of the century, at least in the larger cities, water supplies were usually safe. Food-borne infections were also drastically reduced by the enforcement of laws concerned with the preparation, storage, and distribution of food. Insect-borne infections, such as malaria and yellow fever, which were common in tropical and semitropical climates, were eliminated by the destruction of the responsible insects. Fundamental to this improvement in health has been the diminution of poverty, for most public health measures are expensive. The peoples of the developing countries fall sick and sometimes die from infections that are virtually unknown in affluent countries.

Public health services in Britain are organized locally under the National Health Service. The medical officer of health is employed by the local council and is the adviser in health matters. The larger councils employ a number of mostly full-time medical officers; in some rural areas, a general practitioner may be employed part-time as medical officer of health.

The medical officer has various statutory powers conferred by acts of Parliament, regulations and orders, such as food and drugs acts, milk and dairies regulations, and factories acts. He supervises the work of sanitary inspectors in the control of health nuisances. The compulsorily notifiable infectious diseases are reported to him, and he takes appropriate action. Other concerns of the medical officer include those involved with the work of the district nurse, who carries out nursing duties in the home, and the health visitor, who gives advice on health matters, especially to the mothers of small babies. He has other duties in connection with infant welfare clinics, crèches, day and residential nurseries, the examination of schoolchildren, child guidance clinics, foster homes, factories, problem families, and the care of the aged and the handicapped.

Federal, state, county, and city governments all have public health functions. Under the U.S. Department of Health and Human Services is the Public Health Service, headed by an assistant secretary for health and the surgeon general. State health departments are headed by a commissioner of health, usually a physician, who is often in the governor's cabinet. He usually has a board of health that adopts health regulations and holds hearings on their alleged violations. A state's public health code is the foundation on which all county and city health regulations must be based. A city health department may be independent of its surrounding county health department, or there may be a combined city-county health department. The physicians of the local health departments are usually called health officers, though occasionally people with this title are not physicians. The larger departments may have a public health director, a district health director, or a regional health director.

The minimal complement of a local health department is a health officer, a public health nurse, a sanitation expert, and a clerk who is also a registrar of vital statistics. There may also be sanitation personnel, nutritionists, social workers, laboratory technicians, and others.

Japan's Ministry of Health and Welfare directs public health programs at the national level, maintaining close coordination among the fields of preventive medicine, medical care, and welfare and health insurance. The departments of health of the prefectures and of the largest municipalities operate health centres. The integrated community health programs of the centres encompass maternal and child health, communicable-disease control, health education, family planning, health statistics, food inspection, and environmental sanitation. Private physicians, through their local medical associations, help to formulate and execute particular public health programs needed by their localities.

Numerous laws are administered through the ministry's bureaus and agencies, which range from public health, environmental sanitation, and medical affairs to the children and families bureau. The various categories of institutions run by the ministry, in addition to the national hospitals, include research centres for cancer and leprosy, homes for the blind, rehabilitation centres for the physically handicapped, and port quarantine services.

In the aftermath of the dissolution of the Soviet Union, responsibility for public health fell to the governments of the successor countries.

The public health services for the U.S.S.R. as a whole were directed by the Ministry of Health. The ministry, through the 15 union republic ministries of health, directed all medical institutions within its competence as well as the public health authorities and services throughout the country.

The administration was centralized, with little local autonomy. Each of the 15 republics had its own ministry of health, which was responsible for carrying out the plans and decisions established by the U.S.S.R. Ministry of Health. Each republic was divided into oblasti, or provinces, which had departments of health directly responsible to the republic ministry of health. Each oblast, in turn, had rayony (municipalities), which have their own health departments accountable to the oblast health department. Finally, each rayon was subdivided into smaller uchastoki (districts).

In most rural rayony the responsibility for public health lay with the chief physician, who was also medical director of the central rayon hospital. This system ensured unity of public health administration and implementation of the principle of planned development. Other health personnel included nurses, feldshers, and midwives.

For more information on the history, organization, and progress of public health, see below.

The medical services of armies, navies, and air forces are geared to war. During campaigns the first requirement is the prevention of sickness. In all wars before the 20th century, many more combatants died of disease than of wounds. And even in World War II and wars thereafter, although few died of disease, vast numbers became casualties from disease.

The main means of preventing sickness are the provision of adequate food and pure water, thus eliminating starvation, avitaminosis, and dysentery and other bowel infections, which used to be particular scourges of armies; the provision of proper clothing and other means of protection from the weather; the elimination from the service of those likely to fall sick; the use of vaccination and suppressive drugs to prevent various infections, such as typhoid and malaria; and education in hygiene and in the prevention of sexually transmitted diseases, a particular problem in the services. In addition, the maintenance of high morale has a striking effect on casualty rates, for, when morale is poor, soldiers are likely to suffer psychiatric breakdowns, and malingering is more prevalent.

The medical branch may provide advice about disease prevention (preventive medicine), but the actual execution of this advice is through the ordinary chains of command. It is the duty of the military, not of the medical, officer to ensure that the troops obey orders not to drink infected water and to take tablets to suppress malaria.

In a war zone, medical officers have an aid post where, with the help of corpsmen, they apply first aid to the walking wounded and to the more seriously wounded who are brought in. The casualties are evacuated as quickly as possible by field ambulances or helicopters. At a company station, medical officers and medical corpsmen may provide further treatment before patients are evacuated to the main dressing station at the field ambulance headquarters, where a surgeon may perform emergency operations. Thereafter, evacuation may be to casualty clearing stations, to advanced hospitals, or to base hospitals. Air evacuation is widely used.

In peacetime most of the intermediate medical units exist only in skeleton form; the active units are at the battalion and hospital level. When physicians join the medical corps, they may join with specialist qualifications, or they may obtain such qualifications while in the army. A feature of army medicine is promotion to administrative positions. The commanding officer of a hospital and the medical officer at headquarters may have no contacts with actual patients.

Although medical officers in peacetime have some choice of the kind of work they will do, they are in a chain of command and are subject to military discipline. When dealing with patients, however, they are in a special position; they cannot be ordered by a superior officer to give some treatment or take other action that they believe is wrong. Medical officers also do not bear or use arms unless their patients are being attacked.

Naval medical services are run on lines similar to those of the army. Junior medical officers are attached to ships or to shore stations and deal with most cases of sickness in their units. When at sea, medical officers have an exceptional degree of responsibility in that they work alone, unless they are on a very large ship. In peacetime, only the larger ships carry a medical officer; in wartime, destroyers and other small craft may also carry medical officers. Serious cases go to either a shore-based hospital or a hospital ship.

Flying has many medical repercussions. Cold, lack of oxygen, and changes of direction at high speed all have important effects on bodily and mental functions. Armies and air forces (United States Air Force, The) may share the same medical services.

A developing field is aerospace medicine. This involves medical problems that were not experienced before spaceflight, for the main reason that humans in space are not under the influence of gravity, a condition that has profound physiological effects.

The remarkable developments in medicine that have been brought about in the 20th century, especially since World War II, have been based on research either in the basic sciences related to medicine or in the clinical field. Advances in the use of radiation, nuclear energy, and space research have played an important part in this progress. Some laypersons often think of research as taking place only in sophisticated laboratories or highly specialized institutions where work is devoted to scientific advances that may or may not be applicable to medical practice. This notion, however, ignores the clinical research that takes place on a day-to-day basis in hospitals and doctors' offices.

Although the most spectacular changes in the medical scene during the 20th century, and the most widely heralded, have been the development of potent drugs and elaborate operations, another striking change has been the abandonment of most of the remedies of the past. In the mid-19th century, persons ill with numerous maladies were starved (partially or completely), bled, purged, cupped (by applying a tight-fitting vessel filled with steam to some part and then cooling the vessel), and rested, perhaps for months or even years. Much more recently they were prescribed various restricted diets and were routinely kept in bed for weeks after abdominal operations, for many weeks or months when their hearts were thought to be affected, and for many months or years with tuberculosis. The abandonment of these measures may not be thought of as involving research, but the physician who first encouraged persons who had peptic ulcers to eat normally (rather than to live on the customary bland foods) and the physician who first got his patients out of bed a week or two after they had had minor coronary thrombosis (rather than insisting on a minimum of six weeks of strict bed rest) were as much doing research as is the physician who first tries out a new drug on a patient. This research, by observing what happens when remedies are abandoned, has been of inestimable value, and the need for it has not passed.

Much of the investigative clinical field work undertaken in the present day requires only relatively simple laboratory facilities because it is observational rather than experimental in character. A feature of much contemporary medical research is that it requires the collaboration of a number of persons, perhaps not all of them doctors. Despite the advancing technology, there is much to be learned simply from the observation and analysis of the natural history of disease processes as they begin to affect patients, pursue their course, and end, either in their resolution or by the death of the patient. Such studies may be suitably undertaken by physicians working in their offices who are in a better position than doctors working only in hospitals to observe the whole course of an illness. Disease rarely begins in a hospital and usually does not end there. It is notable, however, that observational research is subject to many limitations and pitfalls of interpretation, even when it is carefully planned and meticulously carried out.

The administration of any medicament, especially a new drug, to a patient is fundamentally an experiment: so is a surgical operation, particularly if it involves a modification to an established technique or a completely new procedure. Concern for the patient, careful observation, accurate recording, and a detached mind are the keys to this kind of investigation, as indeed to all forms of clinical study. Because patients are individuals reacting to a situation in their own different ways, the data obtained in groups of patients may well require statistical analysis for their evaluation and validation.

One of the striking characteristics in the medical field in the 20th century has been the development of new drugs, usually by pharmaceutical companies. Until the end of the 19th century, the discovery of new drugs was largely a matter of chance. It was in that period that Paul Ehrlich, the German scientist, began to lay down the principles for modern pharmaceutical research that made possible the development of a vast array of safe and effective drugs. Such benefits, however, bring with them their own disadvantages: it is estimated that as many as 30 percent of patients in, or admitted to, hospitals suffer from the adverse effect of drugs prescribed by a physician for their treatment (iatrogenic disease). Sometimes it is extremely difficult to determine whether a drug has been responsible for some disorder. An example of the difficulty is provided by the thalidomide disaster between 1959 and 1962. Only after numerous deformed babies had been born throughout the world did it become clear that thalidomide taken by the mother as a sedative had been responsible.

In hospitals where clinical research is carried out, ethical committees often consider each research project. If the committee believes that the risks are not justified, the project is rejected.

After a potentially useful chemical compound has been identified in the laboratory, it is extensively tested in animals, usually for a period of months or even years. Few drugs make it beyond this point. If the tests are satisfactory, the decision may be made for testing the drug in humans. It is this activity that forms the basis of much clinical research. In most countries the first step is the study of its effects in a small number of health volunteers. The response, effect on metabolism, and possible toxicity are carefully monitored and have to be completely satisfactory before the drug can be passed for further studies, namely with patients who have the disorder for which the drug is to be used. Tests are administered at first to a limited number of these patients to determine effectiveness, proper dosage, and possible adverse reactions. These searching studies are scrupulously controlled under stringent conditions. Larger groups of patients are subsequently involved to gain a wider sampling of the information. Finally, a full-scale clinical trial is set up. If the regulatory authority is satisfied about the drug's quality, safety, and efficacy, it receives a license to be produced. As the drug becomes more widely used, it eventually finds its proper place in therapeutic practice, a process that may take years.

An important step forward in clinical research was taken in the mid-20th century with the development of the controlled clinical trial. This sets out to compare two groups of patients, one of which has had some form of treatment that the other group has not. The testing of a new drug is a case in point: one group receives the drug, the other a product identical in appearance, but which is known to be inert—a so-called placebo. At the end of the trial, the results of which can be assessed in various ways, it can be determined whether or not the drug is effective and safe. By the same technique two treatments can be compared, for example a new drug against a more familiar one. Because individuals differ physiologically and psychologically, the allocation of patients between the two groups must be made in a random fashion; some method independent of human choice must be used so that such differences are distributed equally between the two groups.

In order to reduce bias and make the trial as objective as possible the double-blind technique is sometimes used. In this procedure, neither the doctor nor the patients know which of two treatments is being given. Despite such precautions the results of such trials can be prejudiced, so that rigorous statistical analysis is required. It is obvious that many ethical, not to say legal, considerations arise, and it is essential that all patients have given their informed consent to be included. Difficulties arise when patients are unconscious, mentally confused, or otherwise unable to give their informed consent. Children present a special difficulty because not all laws agree that parents can legally commit a child to an experimental procedure. Trials, and indeed all forms of clinical research that involve patients, must often be submitted to a committee set up locally to scrutinize each proposal.

In drug research the essential steps are taken by the chemists who synthesize or isolate new drugs in the laboratory; clinicians play only a subsidiary part. In developing new surgical operations clinicians play a more important role, though laboratory scientists and others in the background may also contribute largely. Many new operations have been made possible by advances in anesthesia, and these in turn depend upon engineers who have devised machines and chemists who have produced new drugs. Other operations are made possible by new materials, such as the alloys and plastics that are used to make artificial hip and knee joints.

Whenever practicable, new operations are tried on animals before they are tried on patients. This practice is particularly relevant to organ transplants (transplant). Surgeons themselves—not experimental physiologists—transplanted kidneys, livers, and hearts in animals before attempting these procedures on patients. Experiments on animals are of limited value, however, because animals do not suffer from all of the same maladies as do humans.

Many other developments in modern surgical treatment rest on a firm basis of experimentation, often first in animals but also in humans; among them are renal dialysis (the artificial kidney), arterial bypass operations, embryo implantation, and exchange transfusions. These treatments are but a few of the more dramatic of a large range of therapeutic measures that have not only provided patients with new therapies but also have led to the acquisition of new knowledge of how the body works. Among the research projects of the late 20th century is that of gene transplantation, which has the potential of providing cures for cancer and other diseases.

Developments in modern medical science have made it possible to detect morbid conditions before a person actually feels the effects of the condition. Examples are many: they include certain forms of cancer; high blood pressure; heart and lung disease; various familial and congenital conditions; disorders of metabolism, like diabetes; and acquired immune deficiency syndrome (AIDS). The consideration to be made in screening is whether or not such potential patients should be identified by periodic examinations. To do so is to imply that the subjects should be made aware of their condition and, second, that there are effective measures that can be taken to prevent their condition, if they test positive, from worsening. Such so-called specific screening procedures are costly since they involve large numbers of people. Screening may lead to a change in the life-style of many persons, but not all such moves have been shown in the long run to be fully effective. Although screening clinics may not be run by doctors, they are a factor of increasing importance in the preventive health service.

Periodic general medical examination of various sections of the population, business executives for example, is another way of identifying risk factors that, if not corrected, can lead to the development of overt disease.